This invention relates to an improvement in the sandwich method for enzyme immunoassay.
The sandwich method of enzyme immunoassay is an excellent method which has been lately developed as a microassay of substances, as disclosed in Japanese Patent Publication No. 47011/1977, Japanese Patent Application Laid-open Nos. 32114/1977 and 57316/1977, "Igaku no Ayumi (Progress of Medicine)", vol. 102, No. 2, pages 57-65, and the like. This is being employed mainly for measuring antigenic substances, such as .alpha.-fetoprotein, HBs antigens, hormones etc.
On measuring a substance using this sandwich method enzyme immunoassay, while it is possible to separately conduct measurements on the respective specimens, it is more common to conduct measurements collectively on a plurality of specimens in which the same substance is to be detected. When measuring collectively, the plurality of specimens are successively contacted at room temperature with a material which will be specifically combined with the substance to be measured and which has been made in the solid phase, after which they are reacted at a temperature ranging from room temperature to 45.degree. C. and subjected to the subsequent steps to complete the measurement. However, in this case, there is a disadvantage wherein a great fluctuation occurs in the results. This is the reason why, since the plurality of specimens is successively contacted with the material which will be specifically combined with the substance to be measured and which has been made in the solid phase, there is a considerable time lag between the specimen contacted first and the specimen contacted last. Such a time lag is the greatest in the above step, although some lag in time is also inevitably produced in the subsequent steps. It is believed that the fluctuation of results is due to this time lag. Therefore, the greater the number of the speciments to be measured at one time, the greater the fluctuation.